Re: [PATCH v8 2/3] net: hisilicon: new hip04 MDIO driver

[zhangfei <zhangfei.gao@linaro.org>]

On 04/22/2014 02:21 AM, Sergei Shtylyov wrote:
> On 04/21/2014 10:03 PM, Florian Fainelli wrote:
>
>>>> Hisilicon hip04 platform mdio driver
>>>> Reuse Marvell phy drivers/net/phy/marvell.c
>
>>>> Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
>>> [...]
>
>>>> diff --git a/drivers/net/ethernet/hisilicon/hip04_mdio.c
>>>> b/drivers/net/ethernet/hisilicon/hip04_mdio.c
>>>> new file mode 100644
>>>> index 0000000..19826a3
>>>> --- /dev/null
>>>> +++ b/drivers/net/ethernet/hisilicon/hip04_mdio.c
>>>> @@ -0,0 +1,185 @@
>
> [...]
>
>>>> +static int hip04_mdio_reset(struct mii_bus *bus)
>>>> +{
>>>> +       int temp, err, i;
>>>> +
>>>> +       for (i = 0; i < PHY_MAX_ADDR; i++) {
>>>> +               hip04_mdio_write(bus, i, 22, 0);
>
>>>     Why? What kind of a register this is? <uapi/linux/mii.h> tells me
>>> it's
>>> MII_SREVISION...
>
>> I think this rather means clause 22 as opposed to clause 45.
>
>     No, the corresponding hip04_mdio_write()'s parameter is a register
> #, so this is a write of 0 to register #22. A comment certainly wouldn't
> hurt here...

It's private register of the phy marvell 88e1512.
To make it clearer using define instead.
#define MII_MARVELL_PHY_PAGE    22

The registers has been grouped into several pages, access register need 
choose which page first.
>
>>>> +               temp = hip04_mdio_read(bus, i, MII_BMCR);
>
>>>     You're not checking for error...
>
>>>> +               temp |= BMCR_RESET;
>>>> +               err = hip04_mdio_write(bus, i, MII_BMCR, temp);
>
>>>     Hmm, why you're open coding BMCR reset? There's phy_init_hw()
>>> doing this
>>> correctly...
>
>> Except that this runs way before we have created the PHY driver, so we
>> can't use that function just yet.
>
>     Ah, you're right.
>
>> I already asked about this, and he
>> explained that this was because the PHY devices he uses are not
>> responding correcty to MII_PHYSID1/2 reads.
>
>     So, this manual reset loop helps with reading the ID registers? A
> comment wouldn't hurt either...
Yes, it required for get_phy_id, will add comments.

>
>>>> +               if (err < 0)
>>>> +                       return err;
>
>     I'm not at all sure we want to leave the reset loop on a first write
> error.
Yes, continue can be used instead.

>
>>>> +       }
>>>> +
>>>> +       mdelay(500);
>
>     I'm not sure this is enough, given that in phy_init_hw() we poll for
> 600 ms + 1 ms.
Though not find clear delay time required from the phy spec, the 
experiment shows OK.
Also here can not verify the BMCR_RESET bit, 0xffff will returned if the 
phy is not exists.
>
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int hip04_mdio_probe(struct platform_device *pdev)
>>>> +{
>>>> +       struct resource *r;
>>>> +       struct mii_bus *bus;
>>>> +       struct hip04_mdio_priv *priv;
>>>> +       int ret;
>>>> +
>>>> +       bus = mdiobus_alloc_size(sizeof(struct hip04_mdio_priv));
>>>> +       if (!bus) {
>>>> +               dev_err(&pdev->dev, "Cannot allocate MDIO bus\n");
>>>> +               return -ENOMEM;
>>>> +       }
>>>> +
>>>> +       bus->name = "hip04_mdio_bus";
>>>> +       bus->read = hip04_mdio_read;
>>>> +       bus->write = hip04_mdio_write;
>>>> +       bus->reset = hip04_mdio_reset;
>
>>>     Ah... However I don't think it a good implementation of that bus
>>> method...
>
>     I assumed this method exists to do a hardware reset of the whole
> bus, not to do a loop of soft-resetting all PHYs...
>

It is required for each phy, if no such reset, the specific phy can NOT be
detected and get_phy_id returns 0.

Thanks